1. Field of the Invention
2. Description of the Related Art
Clock generators have been in use for years. Typically, clock generators are comprised of chips from semiconductor companies that utilize Spread Spectrum technology. This technique is used to reduce the electromagnetic interference (EMI).
Main problem with conventional clock generators is that the high frequency of the clock signal causes increased EMI. When the spread spectrum technique is used to reduce the EMI, jitter is introduced in the clock signal which may impact the circuit operation. Another problem with conventional clock generators that use the spread spectrum technique is that the emission reduction can only reach to about −10 dB. Another problem with conventional clock generators that use the spread spectrum technique is that the circuit complexity is increased when compared with clock generators that do not employ the spread spectrum technique.
While these devices may be suitable for the particular purpose to which they address, they are not as suitable for reducing emission of any given signal. This is accomplished by manipulating the signal and recovering the original signal.
U.S. Pat. No. 6,292,507 B1 discloses a spread spectrum clock generator circuit which automatically compensates for the variation in passive component values and system gain and charge pump current in the phase locked loop. This clock generator is a single chip generator. Modified clock has jitter and the reduction in EMI is limited.
U.S. Pat. No. 6,647,052 discloses generation of a spread spectrum master clock and plurality of phase-offset spread spectrum slave clocks. Different phase offsets are generated using phase delays. These phase delays are either predetermined or calculated dynamically. This clock generator provides limited EMI reduction.
U.S. Pat. No. 6,975,148 discloses a spread spectrum clock generator. The design uses current control oscillator. The clock generator has limited EMI reduction. It introduces jitter in the modified clock signal.
U.S. Pat. No. 7,095,260 B2 discloses a spread spectrum clock generator that uses single chip to generate a spread spectrum clock.
These patents mentioned above each uses single chip to generate spread spectrum clock which has jitter.
In these respects, the low emission signal manipulating circuit according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for the purpose of reducing emission of a given signal by using a transmitter and multiple receivers. Transmitter modifies the signal to lower the electromagnetic emission and receivers recover the original signal.